Food products whose qualities and prices vary depending upon production locations are usually sold with an attached label etc. displaying its production location. A purchaser chooses a food product to buy, based on such information displayed on a label etc. Moreover, when qualities and prices of food products vary depending upon freshness degrees, a label etc. displaying a date of manufacture and an eat-by freshness date is similarly referred to. Thus, labels conventionally attached to food products only display information about the food products, such as production locations and freshness degrees.
As a method of a consumer's (purchaser's) objectively examining a production location of a product: a code issue request device located at the production location of the product, at the time of the product shipment, measures its own located position, and requests a production location guarantee device to issue a production location guarantee code including position information indicating the result of measuring the position and time information indicating the time of measuring the position; the production location guarantee device generates the production location guarantee code by performing encryption processing to the position information and the time information, and transmits the generated code to the code issue request device; the code issue request device attaches a code seal displaying the production location guarantee code to a product to be circulated in the market; as to the product with the attached code seal, a consumer transmits a production location checking request including the production location guarantee code displayed on the code seal, from a terminal device; the production location guarantee device performs decryption processing to the production location guarantee code to acquire the position information and the time information, and transmits a production location check message indicating the acquired position information and time information to the terminal device (refer to Patent Document 1, for example).
As a method of verifying time, it is known to the public to generate synthetic information from time information indicating time and temporal change information (for example, weather data) being verification information of the time information and changing in accordance with time progresses, and to use this synthetic information for verification (refer to Patent Document 2, for example). The same can be said for a method of verifying position. As a service practically using this method, COCO-DATES (registered trademark) service (website URL <http://www.mitsubishielectric.co.jp/coco-dates/>) can be cited, for example.    [Patent Document 1] Japanese Unexamined Patent Publication No. 2005-107799    [Patent Document 2] Patent Publication No. 3475145